Fill a small bowl with ice-cold water and have it next to the hob. Grease and line an 18cm-square cake tin with baking paper.
Put the sugar, cream and butter in a large, heavy-based saucepan. Heat gently until all the sugar has dissolved and the butter has melted, then increase the heat and bring to the boil. Boil, without stirring, for 8-10 minutes. Test the mixture is done by dropping a little into the cold water – it should set into a ‘soft ball’ consistency.
Remove the pan from the heat and allow the fudge to sit for 5 minutes. Beat in the vanilla using a wooden spoon, then beat for a further 4-5 minutes until thickened. Pour into the prepared tin and sprinkle over the chocolate chips, stars and sprinkles. Allow the fudge to completely cool, then chill in the fridge for 2 hours until set. Cut into small squares to serve or package up as gifts.